It is proposed to study gas exchange during anesthesia and operation with emphasis upon both whole body metabolic requirements and adequacy of circulatory and respiratory performance. In addition, the effects of anesthesia upon gas exchange will be determined for individual organs including the brain, skeletal muscle, and splanchnic circulation. The approach includes clinical studies in man, experimental laboratory work with dogs, development of methods for analysis of biological fluid and gas samples, and demonstration of clinical applications when indicated. A better understanding of the determinants of tissue O sub 2 levels during anesthesia is our ultimate area of interest.